Lateral flow assays (LFA) have been used successfully as a diagnostic tool for more than 15-years. They provide point of care (POC) diagnosis without requiring expansive clinical laboratories and specifically trained technical staff. LFA devices are generally considered inexpensive to manufacture, have long shelf-lives and have minimal storage requirements. LFA diagnostic results are read either through visual inspection of the chromatographic strip or through the use of a spectrophotometer ‘reader’ instrument. Visual inspection of the assay results is typically limited to a yes/no or positive/negative result.
Both visual and reader measurements are considered qualitative or semi-quantitative and not sensitive enough to quantitatively assess low-abundance biomarker levels. Current LFA designs for POC use are also limited due to their inability to precondition complex biological fluids prior to immunoassay analysis. These limitations reduce LFAs sensitivity for low abundance analytes and biomarkers while, concurrently, minimizing their effectiveness as a POC diagnostic device for low abundance biomarkers, and other low molecular weight compounds.
A major challenge when using a POC immunoassay as a diagnostic device is the ability to process complex biological fluids without standard lab equipment. In many cases, a centrifuge may be required to pre-condition blood samples to provide a plasma sample or to remove cells from blood samples. Incorporation of coreshell hydrogel nanoparticles with molecular sieving and target analyte sequestration provides a unique solution to this limitation. Hydrogel nanoparticles designed with specific sieving and affinity characteristics act as a filter, concentrator, and protector of target analytes from degradation prior to analysis. These functions offer a novel solution to address major analytical challenges in biomarker discovery and diagnostic assays for low abundance analytes.
Another major challenge for LFA devices are their sensitivity for specific analytes of interest. The inability to precondition samples prior to analysis leads to poor sensitivity, high background interference and diluted samples. Incorporation of hydrogel nanoparticles into the device as a means of sample preconditioning significantly improves sensitivity by sequestering and concentrating only the targeted analyte prior to extraction from the particles into the immunoassay.